This invention relates to fabricated construction panels, and in particular to such panels which are formed by mixing a plurality of substances and forming the mixture into a layer which is placed on a supporting surface and caused to set and thereby form a panel which can be used for structural purposes. One such construction panel known to the art is formed of a combination of inorganic magnesium compounds, water and other substances which, after being mixed, is extruded onto a supporting surface and is then permitted to stand for a period of time while the extruded slurry sets into relatively rigid form. During that setting the extruded layer tends to slump at the edges, so that the edge portions thus produced diminish in thickness, usually progressively toward the edge. Construction panels must usually be provided with uniform thickness, and hence once the slurry has set it becomes necessary to cut off and discard those edge portions of diminishing or diminished thickness. This represents economic waste which contributes to the manufacturing cost of the panels. Thus minimization of the slurrying tendency of the material is highly to be desired.
Specifically, a construction panel with square edges and with substantially desirable propertiesxe2x80x94e.g., it is non-combustible, does not disintegrate when immersed in water, does not support insect life, is non-nutrient to mold or fungus, and has desirable strength propertiesxe2x80x94has been formed by mixing magnesium oxide, magnesium chloride, talcum powder, wood bran, and glass fiber cloth with water and a catalyst agent, and the viscous slurry thus produced is extruded onto a supporting form such as a sheet of plastic and permitted to set. Slumping occurs at the edges, and because construction panels must, as a general matter, have square edges, the slumped edge portions of the set panel must be removed, with consequent economic loss.
I have discovered that the degree of slumping which this type of material will exhibit during setting may be very significantly reduced by the addition to the slurry, before the material is extruded, of a small amount of plastic fibers on the order of about 0.1 percent by weight of the entire slurry. The additional cost involved in adding these fibers is insignificant compared to the savings which result from having to cut away and discard smaller slumped edges of the extruded sheet.